In order to accomplish reliable and valid research into the characteristics and mechanisms of Alzheimer's disease (AD) and related dementias, it is imperative to have data available form a well-characterized cohort of patients. The cohort should have a broad range of levels of education and socioeconomic status as well as racial diversity. It should contain patients with varying levels of disease severity including, what has become known as Mild Cognitive Impairment or dementia prodrome. A system must be in place for reconsideration and annual update of diagnoses based on new clinical information such that a complete series of clinical impressions can be recovered over the course of the disease. Such a flexible system is also essential to accommodate and review cases based on new research practices such as the diagnostic criteria for Dementia with Lewy Bodies. The Clinical Core of the Alzheimer's Disease Research Center at the University of Pittsburgh fulfills these functions. The Clinical Core provides evaluation and follow-up to patients and control subjects followed in the Memory Disorders Clinic and enrolled in the ADRC Registry. Specifically, the ore provides a detailed evaluation of all patients and control subjects at study entry, and at annual evaluations until the subject drops from the project or dies. The Core also strives towards maximal participation in the autopsy program of the ADRC by providing longitudinal follow-up to these patients and controls. It is also responsible for providing clinical data, research subjects (patients and control subjects), training, and technical and scientific leadership for support of new and ongoing research at the Pittsburgh ADRC and associated local, regional, national, and international studies. Finally, the ADRC will continue outreach programs developed to provide care and support for members of the medically under-served inner-city populations. The ADRC's satellite clinic, the Alzheimer Outreach Center (AOC) in the predominantly African American Hill District of Pittsburgh, evaluates and enrolls patients and control subjects in the ADRC Registry. Special programs to education the African American community are also part of this program. External confirmation of the accuracy of the clinical diagnosis of AD is also vital to ensure that the evolving diagnostic procedures employed by the Clinical Core are appropriate. Autopsy confirmation of a clinical diagnosis of Probable AD was 98% for all cases from the ADRC coming to autopsy since the inception of the Center.